Lung diseases that arise from injury to or defective development of the pulmonary epithelium including COPD, emphysema, pulmonary fibrosis, and bronchopulmonary dysplasia cause significant morbidity and mortality. Despite intense interest in the possibility of using lung stem/progenitor cells to reverse the course of disease in animal models the field is still in its infancy. My lab has generated a novel Doxycycline (Dox) regulated transgenic mouse model in which expression of a dominant negative Nuclear Factor I (NFIen) transgene induces adult type II cells to dedifferentiate and proliferate forming clusters of progenitor like cells protruding into the alveolar space. Upon Dox withdrawal these cells re-differentiate into both proximal and distal lineages. In this exploratory R21 project the effect of time On Dox on differentiation capacity of these cells will be determined in vivo. Proliferation and differentiation capacity of isolated cells will be determined in vitro and their potential for tumorigenesis tested in the nude mouse assay. The ability of NFIen reprogrammed progenitor cells to participate in pneumonectomy induced compensatory lung growth will be measured by morphometric analysis. Aim 2 will determine the signaling pathway(s) that are required for NFIen mediated reprogramming. Preliminary data shows that the cell clusters express high levels of (-catenin and E-cadherin. We will test the hypothesis that NFIen induces Wnt signaling and determine whether activated (-catenin is required for either cluster formation or differentiation of the cells upon dox withdrawal. An unbiased parallel approach of microarray analysis of lungs and/or cells On and Off Dox will generate new data on the pathways that are regulated by NFI to induce progenitor cell expansion and differentiation. Knowledge of the pathways repressed/activated in our novel transgene driven system will provide the basis for new approaches to induce the expansion of lung epithelial progenitor cells and their subsequent differentiation into specific cell lineages for cell-based therapies so that promising advances eventually can be applied clinically. PUBLIC HEALTH RELEVANCE: Lung diseases that arise from injury to or defective development of the pulmonary epithelium including COPD, emphysema, pulmonary fibrosis, and bronchopulmonary dysplasia cause significant morbidity and mortality. Current treatment modalities for these serious lung diseases are not adequate and new approaches are necessary. The research proposed in this R21 will develop a novel model of adult mouse lung epithelial stem cell expansion in vivo and in vitro, and will set the groundwork for developing new approaches to expanding lung epithelial progenitor cells for use in cell based therapies for lung disease.